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Rabid animals on the rise as human vaccine supply tightens

It’s been a wild year for rabies in the U.S, with rising reports of the disease in animals -- think rabid skunks, bats, even beavers -- just as supplies of the vaccine used to treat humans for the deadly virus are down.

“We’ve had essentially a lack of a winter, a very warm summer and reports of animal rabies are up,” said Jesse Blanton, an epidemiologist with the Centers for Disease Control and Prevention.

Though no firm figures are available, Blanton estimates that the number of rabid animals confirmed in the U.S. will reach the upper margins of the 6,000 to 7,000 typically found in a year. In 2011, the number barely topped 6,000.

“We had a much earlier start to the bat season this year,” he said. “It was a month early in some places. It’s really been across the board.”

No human cases of rabies infection have been reported in the U.S. this year, though six cases were reported in 2011, a high number in a country that typically sees only one or two. Three of those cases were in people who had contact with rabid animals in other countries.

But the number of human exposures to rabid animals seems to be higher this year, even in a country where up to 100 cases of possible contact may be reported across the nation on a typical summer day. And some of the cases have been sensational enough to make headlines:

“It’s been a more intense summer for reports of human contacts,” Blanton said. However, the increased contact comes just as the two manufacturers of rabies vaccine in the U.S. -- Novartis and Sanofi Pasteur -- are reporting limited supplies and no clear date for resolution.

CDC officials have stopped short of calling the problem a shortage, but there’s no question supplies are thin. The agency reported last week that Novartis’ RabAvert, a rabies vaccine for pre-exposure use, is available only from wholesale distributors who already had existing stock. And the CDC advised that while supplies of vaccine for post-exposure prophylaxis, or PEP, remain available, health officials should make sure that rabies shots go only to those who need them.

“It’s a little worrisome. It makes us even more cautious,” said Dr. Paul Ettestad, New Mexico’s state health veterinarian. “Usually we keep enough vaccine on hand for 10 people and right now we have enough only for three or four.”

Sixty people in New Mexico have had to be treated this year with rabies post-exposure prophylaxis, or PEP, after coming into contact with rabid animals, including domestic pets, Ettestad said. An outbreak of the disease that began in December has been concentrated in Eddy County in the south part of the state.

Typically, between 30 and 70 people are treated in New Mexico in an entire year with the PEP series that includes a dose of human rabies immune globulin and four doses of vaccine given over two weeks.

Overall in the U.S., between 23,000 and 38,000 people receive PEP vaccinations after confirmed or possible exposure to rabid animals each year.

This year's combination of high demand and low vaccine supply has created sporadic problems across the country, said Blanton.

“A crimped supply is a good way to refer to it,” he said. “Largely it appears to be a short delay that happened within the distribution chain of the vaccines.”

That means that although there may be enough rabies vaccine to go around, it may take longer or be more complicated to get it. In Illinois, for instance, several providers had difficulty acquiring rabies vaccine PEP for patients with rabies exposure, according to Melaney Arnold, a health department spokeswoman. 

CDC officials said they believe the smoother distribution will resume soon, but the American Society of Health-System Pharmacists, which tracks the nation’s drug shortages, reported that neither Novartis nor Sanofi Pasteur could estimate when the products would be available.

This isn’t the first -- nor the worst -- “crimp” in the supply of rabies vaccine. An outright shortage in 2009 rippled through the rabies community, forcing states to implement secret passwords to gain access to vaccine and leading to a reevaluation of how many doses of vaccine were actually needed to prevent infection. In 2010, the CDC's Advisory Committee on Immunization Practices, or ACIP, agreed to reduce the number of doses from five to four.

The situation is not that dire now, but health care providers are urged to closely evaluate rabies cases before prescribing vaccine.

“We’ve never had the recommendation that there’s carte blanche that everyone needs to be vaccinated,” Blanton said. “We are expecting a normal, healthy, cognizant person to be aware if they had contact with a bat.”

In practice, however, determining whether contact actually occurred is harder than it seems. In Kentucky earlier this year, state health officials had to interview more than 260 people who worked as volunteers at a charity service organization and wound up sleeping in an old schoolhouse infested with bats.

“We categorized everyone as low risk, moderate risk or high risk,” said Dr. Kraig Humbaugh, the Kentucky state epidemiologist. “Instead of a blanket recommendation, we were being judicious with our vaccine administration.”

Sixteen of the volunteers were advised to consult with their doctors about PEP because they had known contact with a bat. Others were pointed toward treatment because they’d slept in a room where a bat was found. Rabies is primarily spread through the infected saliva of an animal, usually through bites. The fear is that certain people -- those who sleep too soundly, those on medication, the disabled and children -- might not realize it if they've been bitten by a bat. Still others might not feel the sting of the bat's sharp teeth.

In 2011, two of the U.S. rabies victims didn’t report contact with bats, but both had reported waking to find bats in their bedroom. Both later developed the disease and died, a CDC report said.

When in doubt, health officials usually err on the side of vaccination, experts said. The incubation period for rabies  is typically one to three months, but it can vary widely, from less than a week to more than a year, according to the World Health Organization.

The rabies vaccine PEP is the only way to stop the infection, and only during the incubation period. After that, the horrific symptoms progress rapidly, often including fever, pain, agitated behavior, hyperactivity and hydrophobia -- difficulty swallowing and panic at the thought of water. The disease is almost always fatal.

Rabies exposure typically wanes after the first frost, said Blanton, who is looking forward to colder weather. Vaccine supplies should become more plentiful, too.

“Additional lots are already coming down,” he said. “We should be back to normal.”

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